Fire resistant hydraulic fluid



United States Patent 3,272,747 FIRE RESESTANT HYDRAULIC FLUID William T. Shepherd, Port Arthur, Tex., assignor to Texaco Inc, New York, N.Y., a corporation of Delaware No Drawing. Filed June 12, 1963, Ser. No. 287,213 6 Claims. (Cl. 252-78) This invention relates to a the resistant hydraulic fluid. More particularly, it concerns a water-in-oil emulsion possessing outstanding properties for transmitting power in a hydraulic system. This invention is an improvement over commonly assigned copending application Serial No. 198,438 filed on May 29, 1962.

Mineral hydraulic oils employed in industrial plants constitute a dangerous safety hazard with respect to fires and explosions. Leakage of the mineral oil in the presence of an open flame or rupture of hydraulic lines due to a minor fire or accident has caused numerous costly and extensive losses when the inflammable oil ignited. Recently, hazards of this nature have been minimized or substantially removed by replacing the mineral hydraulic oil with a fire resistant hydraulic fluid wherever possible. More particularly, such hazards have been reduced by employing water-in-oil emulsion hydraulic fluids which have a high level of lubricity for hydraulic fluid service but do not propagate a flame even when contacted with an oxyacetylene torch. The above-noted copending application relates to an effective commercially adopted water-in-oil emulsion hydraulic fluid.

Despite the successes achieved to date, efforts have continued to improve the properties of the water-in-oil emulsion hydraulic fluids so that they can be used in a broader range of applications and functions eifectively even under the most severe operating conditions. These efforts have produced a novel oil-in-water hydraulic fluid having vastly improved properties. More particularly, this hydraulic fluid has outstanding low temperature stability which greatly extends the usefulness of the fluid in applications such as hydraulically operated machine mining equipment commonly employed under severe low temperature conditions. The low temperature stability of the fluid is excellent under storage at the freezing point of water and, surprisingly, this stability obtains even through successive [freeze-thaw cycles. The improved hydraulic fluid also has the property of being substantially non-thickening particularly during the start-up of hydraulic equipment. This property prevents pump damage due to cavitation and greatly extends the pump life in a hydraulic system.

The improved fire resistant hydraulic fluid of this invention is a water-in-oil emulsion comprising from 60 to 40 volume percent of Water in the internal phase and from 40 to 60 volume percent of an oleaginous blend containing a major portion of a mineral oil having a viscosity in the range from 50 to 300 SUS at 100 F. in the external phase, 1 to 12 volume percent of a lipophilic emulsifying agent selected from the group consisting of a fatty acid partial ester of a 6 carbon polyhydrie alcohol monoand dianhydride and mixtures thereof, to 20 volume percent of a hydrophilic emulsifying agent based on the lipophilic emulsifying agent comprising an ethylene oxide C alkyl phenol 'adduct in moi ratios of from to 1 to about 40 to 1, 0.05 to 2.5 volume percent of a concentrate of a mono-hydroxyalkyl 'hydrocarbyl thiophosphonate having the formula:

wherein R is a monovalent hydrocarbyl radical, R and R are hydrogen or a monovalent aliphatic hydrocarbyl radical having 1 to 6 carbon atoms and X is sulfur or a mixture of oxygen and sulfur, and a volatile corrosion inhibitor in an amount suflioient to inhibit corrosion by the emulsion while in the vapor and liquid phases. Preferably, in order to meet the performance standards of inhibited mineral oil hydraulic fluids the emulsion contains a minor amount of an anti-oxidant and of an anti-foam agent in the oil phase of the emulsion.

A high amount of water in the emulsion of the present invention is essential in order to guarantee a fire resistant hydraulic fluid. The present fluid meets the standards of the Spray Ignition Test defined by the military specification designated MIL-F4100. From these tests it has been determined that at least 40 percent water is necessary to produce a satisfactory fire resistant fluid with this oil blend. The upper limit of water, namely 60 percent is a necessary limit to prevent a reversal of the emulsion with an accompanying drastic loss of viscosity. A total content within the range of 40 to 60 percent does not greatly affect the outstanding properties of the emulsion. However, an increase in the water content above the upper limit will increase the viscosity until the point of emulsion reversal occurs.

Any type of mineral oil or mixture thereof is useful in accordance with this invention as long as the viscosity of the oil is in the range of 50 to 300 SUS at F. The preferred type of mineral oil is one having the viscosity from 50 to 100 SUS at 100 'F., a flash ranging from 300 to 375 F. and a pour point of not more than +20 F. Since at least 40 volume percent of water is required to render the emulsion tire resistant, the oil component must meet a low viscosity requirement, so that when mixed with water the resulting fluid is not excessively viscous.

The water-in-oil emulsion is prepared from the oleaginous blend containing the emulsifying agents and additives in admixture with the oil. This blend is agitated while water is added in a small but steady stream. Agitation is continued for a time after the proper amount of water has been added to insure complete formation of the emulsion.

The lipophilic emulsifying agents which were found to be effective in this invention are the fatty acid partial esters of a 6 carbon polyhydric alcohol monoor dianhydride, either alone, or in admixture with the same type of compound, the fatty acid portion of the ester having from 6 to 30 carbon atoms. Examples of lipophilic emulsifying agents include the partial esters of sorbitan, sorwherein R is an alkyl group containing 4 to 24 carbon atoms and n has a value of 10 to 40. Examples of these hydrophilic emulsifying agents include adducts of 10 moles of ethylene oxide and one mole of octylphenol, 10 moles of ethylene oxide and one mole of nonylphenol, 14 moles of ethylene oxide and one mole of Z-ethylhexylwherein R is a monovalent hydrocarbyl radical, R and R" are hydrogen or a monovalent aliphatic hydrocarbon radical containing 1 to 6 carbon atoms and X is sulfur or a mixture of oxygen and sulfur. These compounds are formed from the reaction of an alkylene oxide with a hydrocarbyl thiophosphonic acid in the absence of a catalyst and essentially on an equimolar basis as disclosed in US. 3,087,956. Hydrocarbyl thiophosphonic acids are prepared by the reaction of aromatic hydrocarbons, cyclohydrocarbons and aliphatic hydrocarbons with P 8 at elevated temperatures. Although a wide variety of hydrocarbons are usable as the hydrocarbon reactant, olefinic hydrocarbons containing at least 12 carbon atoms are generally employed although lower molecular weight olefins can also be employed. Mono-olefin polymers, such as isobutylene polymer, butylene polymer, propylene polymer, and co-polymers of mono-olefins, such as propylene-isobutylene co-polymer, are particularly preferred. In general, mono-olefin polymers and co-polymers having an average molecular weight between about 250 and 50,000 are suitable with those having an average molecular weight in the range from about 600 to 5,000 being preferred. Specific preferred compounds effective in this invention are mono (2-hydroxyethyl) hydrocarbyl thiophosphonate, mono (hydroxypropyl) hydrocarbyl thiophosphonate, and mono (hydroxybutyl) hydrocarbyl thiophosphonate conforming to the above general formula wherein the hydrocarbyl radical or R is a polybutene radical having an average molecular weight from about 750 to 1000.

It is convenient to employ the mono (hydroxyalkyl) hydrocarbyl thiophosphonate as a concentrate in an oil solution, the oil being similar to the oil forming the major part of the oleaginous blend. This concentrate can consist of 20 to 50 percent and preferably about 34 percent of the hydrocarbyl thiophosphonate with the balance being oil. The hydrocarbyl thiophosphonate-oil concentrate is generally employed in the range of 0.05 to 2.5 volume percent based on the oleaginous blend with the preferred amount being between 0.1 and 1.0 percent.

It is necessary to incorporate a volatile rust inhibitor to prevent the rusting of the metal parts of the hydraulic system with which the fluid in both liquid and vapor phases comes in contact, although other rust inhibitors may also be used. Effective anti-rust agents include amine nitrates, amine carboxylates and hydroxyalkyl nitromethanes. These compounds are useful in amounts from about 0.05 to 1.0 volume percent based on the oil phase or oleaginous blend of the emulsion. Examples of rust inhibitors include 2-hydroxypropylamine nitrite, isopropylamine nitrite, cyclohexylamine nitrite, diisobutylamine nitrite, triethylamine nitrite, amylamine benzoate, diisopropylamine benzoate, monoethanolamine benzoate, isoamylamine salieylate, tris (hydroxymethyl) nitromethane and the like.

An anti-oxidant is an extremely valuable additive in the emulsion to prevent break-down of the oil phase during extended use. Oxidation of the oil causes it to become excessively acidic and harmfully corrosive. This acidity will also seriously effect the stability of the emulsion. The anti-oxidants which have been found to be effective are the partially or totally hindered phenols. These compounds are characterized by the presence of particular organic groups in a certain position on the phenolic portion of the molecule which serves to inhibit a reaction or cause steric hindrance. Effective compounds are represented by the following structural formula:

I l/I wherein R, R, R" and R' represent hydrogen, alkyl and aralkyl and wherein at least one of the groups in the ortho position relative to the oxy group contains at least 3 carbon atoms. Examples of these compounds include:

4-methyl-2,6-di-t-butylphenol;

2-t-butyl-4,6-dimethylphenol;

2,4,6-t-tributylphenol;

2,6-di-t-amyl-4-t-butylphenol;

2,4-dimethyl-6-propylphenol;

t-butyl ether of o-sec-butyl-p-cresol;

t-butyl ether of o-sec-butyl-p-ethylphenol;

t-amyl ether of o-sec-butyl-p-isobutylphenol;

mixtures of oand p-polyalkylbenzylphenol;

1,1-bis(2-hydroxy-3 -t-butyl-5-methylphenyl ethane;

2,2-bis(2-hydroxy-3-t-butyl-5-methylphenyl)n-propane;

l,1-bis(2-hydroxy-3 ,5 -di-t-butylphenyl) n-butane 2,2-bis(2-hydroxy-3,S-di-t-butylphenyl)n-butane;

2,2-bis (2-hydroxy-3-t-butyl-5-methylphenyl) -2-tri-fluorethane;

1,l-bis(2-hydroxy-3,5-di-t-butylphenylmethane.

The water-in-oil emulsions of the invention may at times be employed under conditions which tend to promote foaming. Thus, it is desirable to employ an antifoam additive preferably a dimethyl silicone concentrate, i.e. a 10 percent solution of dimethyl silicone in kerosene. This is generally added to the oil phase in an amount ranging from about to 200 p.p.m.

Anti-Wear agents are often advantageously included in hydraulic fluids, such as the oil-in-Water emulsion of the invention. Suitable anti-wear agents are the hydrocarbon phosphate esters. Effective examples of these compounds are diand triphenyl phosphates, tricresyl phosphate, tributyl phosphate, triethyl phosphate and mixtures of monoand di-alkyl phosphoric acid esters wherein the alkyl group is a straight chain containing from 8 to 16 carbon atoms. The anti-wear agents are generally incorporated in amounts ranging from 0.5 to 10 volume percent based on the mineral oil. The preferred anti-wear agent is tricresyl phosphate which is generally employed in the amount of about 5 volume percent based on the oleaginous blend.

The following examples show the properties of the water-in-oil emulsion of the invention under severe storage conditions and their viscosity behavior in pump tests. Hydraulic Fluid A, representative of this invention, consisted of 40 volume percent water, 60 volume percent of an oleaginous base blend and 500 p.p.m. of tris-(hydroxymethyl) nitromethane. The base blend consisted of 93 percent mineral oil, 5.6 percent sorbitan monooleate, 0.36 percent of the ethylene oxide adduct of nonylphenol in the mole ratio of 30 moles ethylene oxide to 1 mole of nonylphenol, 0.5 percent of mono-(B-hydroxyethyl) polybutene thiophosphonate concentrate in which the polybutene radical had a mean molecular weight of about 940, 0.28 percent of 4-rnethyl-2,6-di-butylphenol, 0.35 percent of 2-hydroxypropylamine nitrite, and p.p.m. of dimethylsilicone polymer concentrate. The mineral oil was a mixture of 23 percent paraffin base oil having an SUS viscosity at 100 F. of about 70 and 70 percent paraflin base oil having an SUS viscosity at 100 F. of about 100.

The foregoing emulsion was compared to a similar water-in-oil emulsion, Hydraulic Fluid B, which diflered essentially from Fluid A in that it contained none of the mono-(B-hydroxyethyl) polybutene thiophosphonate.

In Table I, the storage stability of the fluids is given as determined at room temperature and at 32 F. The fluids were stored for the indicated periods in containers having vertically spaced spigots or taps for drawing samples. The water content and viscosity of the different layers were determined.

Table I.St0rage stability of hydraulic fluids Fluid B Fluid A Percent Vis. SUS Percent Vis. SUS H2O at 100 F. H2O at 100 F.

2 Weeks:

Room Temp.

Spigot #1 42 488 42 515 44 516 44 514 44 516 8 Weeks:

Room Temp;

Spigot #1- 7 111 38 315 2 44 352 40 324 56 515 43 339 56 601 43 331 62 796 43 332 This test shows that the water in the water-in-oil emulsion settled rapidly in Fluid B leading to a breakdown of this emulsion as compared to Fluid A which contained the thiophosphonate additive. The viscosity of Fluid B, moreover, varied substantially at the various liquid levels showing the tendency to instability of this fluid.

The stability of the fluids and particularly their tendency to separate into oil, cream and water phases was determined at 32 F., room temperature, 130 F., at alternate 32 F. and room temperature, and under freezethaw conditions. The percentage of each phase that sepa- 6 This example demonstrates the ability of the waterin-oil emulsion of the invention to retain its emulsion characteristics under most severe temperature conditions over prolonged periods of time in contrast to Fluid B.

The thickening properties of the hydraulic fluids were also compared by determining their Brookfield Viscosity both immediately after the emulsions were prepared and after they had thickened due to standing. These data are presented in Table III below.

Table III.Thickening properties 0 the hydraulic fluids Fluid B Fluid A Original Thickencd Original Thickened API Gravity 20.6 20.3 20.8 20.8 Temp., F 7s s3 s1 82 Brookfield Viscosity, Cps.

N0. 2 Spindle, r.p.m.:

The viscosity of Fluid B immediately following preparation of the emulsion and after it had thickened on standing exhibited a surprising range in viscosity over the diiferent spindle speeds. This is the behavior which causes cavitation during start-up with damage to the hydraulic fluid pumps. Fluid A exhibited substantially no viscosity change over the full range of this test.

Obviously, many modifications and variations of the invention as hereinbefore set 'forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be made as are indicated in the appended claims.

I claim:

1. A fire resistant water-in-oil emulsion suitable for use as a hydrauli fluid comprising from 60 to 40 volume percent of water and from 40 to 60 volume percent of an oleaginous blend containing a major portion of a mineral oil having a viscosity in the range from 50 to 300 SUS at 100 F., from 1 to 12 volume percent of a lipophilic emulsifying agent selected from the group consisting of a fatty acid partial ester of a 6 carbon polyhydric alcohol 'monoand di-anhydride and mixtures thereof, 5 to 20 volume percent of a hydrophilic emulsifying agent based on said lipophilic emulsifying agent comprising an ethylene oxide C alkylphenol adduct in mode ratios of from 10:1 to 40:1, 0.05 to 2.5 volume percent of a concentrate of a mono-(hydroxyalkyl) hydrocarbyl thiophosphonate having the formula:

wherein R is a polyolefin radical having a molecular weight in the range from 250 to 50,000, R and R" are selected from the group consisting of hydrogen and a monovalent aliphatic hydrocarbyl radical having from 1 to 6 carbon atoms and X is selected from the group consisting of sulfur and a mixture of sulfur and oxygen, and a volatile corrosion inhibitor in an amount sufiicient to inhibit corrosion in the liquid and vapor phases.

2. A fire resistant Water-in-oil emulsion suitable for use as a hydraulic fluid comprising from 60 to 40 volume percent of water and from 40 to 60 volume percent of an oleaginous blend containing a major portion of a mineral oil having a viscosity in the range from 50 to 300 SUS at 100 F. from 1 to 12 volume percent of a lipophilic emulsifying agent selected from the group consistof a concentrate of a mono-(hydroxyalkyl) hydrocarbyl thiophosphonate having the formula:

wherein R is a polyolefin radical having a molecular weight in the range from about 600 to 5,000, R and R" are selected from the group consisting of hydrogen and monovalent aliphatic hydrocarbyl radical having from 1 to 6 carbon atoms and X is selected from the group consisting of sulfur and a mixture of sulfur and oxygen, and a volatile corrosion inhibitor in an amount sufficient to inhibit corrosion in the liquid and vapor phases.

3. A fire resistant water-in-oil emulsion suitable for use as a hydraulic fluid comprising from 60 to 40 volume percent of water and from 40 to 60 volume percent of an oleaginous blend containing a major portion of a mineral oil having a viscosity in the range from 50 to 300 SUS at 100 F., from 1 to 12 volume percent of a lipophilic emulsifying agent selected from the group consisting of a fatty acid partial ester of a 6 carbon polyhydric alcohol monoand di-anhydride and mixtures thereof, to 20 volume percent of a hydrophilic emulsifying agent based on said lipophilic emulsifying agent comprising an ethylene oxide C alkylphenol adduct in mole ratios of from 10:1 to 40:1, 0.05 to 2.5 volume percent of a concentrate of a mono-(hydroxyalkyl) hydrocarbyl thiophosphonate having the formula:

wherein R is a polybutene radical having a molecular weight in the range from about 600 to 5,000, R and R are selected from the group consisting of hydrogen and a monovalent aliphatic hydrocarbyl radical having from 1 to 6 carbon atoms and X is selected from the group consisting of sulfur and a mixture of sulfur and oxygen, and a volatile corrosion inhibitor in an amount suflicient to inhibit corrosion in the liquid and vapor phases.

4. A fire resistant water-in-oil emulsion suitable for use as a hydraulic fluid comprising from 60 to 40 volume percent of water and from 40 to 60 volume percent of an oleaginous blend containing a major portion of a mineral oil having a viscosity in the range of 50 to 300 SUS at 100 F., from 4 to 12 volume percent of a lipophilic emulsifying agent selected from the group consisting of fatty acid partial esters of sorbitan and sorbide, 5 to 20 volume percent of a hydrophilic emulsifying agent based on said lipophilic emulsifying agent comprising an ethylene oxide C alkylphenol adduct in mole ratios of from 1021 to 40:1, 0.5 to 2.5 volume percent of a concentrate of a mono-(hydroxyalkyl) hydrocarbyl thiophosphonate having the formula:

wherein R is a polybutene radical having a molecular weight in the range from about 600 to 5,000, R' and R" are selected from the group consisting of hydrogen and a monovalent aliphatic hydrocarbyl radical having from 1 to 6 carbon atoms and X is selected from the group consisting of sulfur and a mixture of sulfur and oxygen, and 0.05 to 1.0 volume percent of a volatile corrosion inhibitor selected from the group consisting of amine nitrites and amine carboxylates.

5. A fire resistant water-in-oil emulsion suitable for use as a hydraulic fluid comprising from to 40 volume percent of water and from 40 to 60 volume percent of an oleaginous blend containing a major portion of a mineral oil having a viscosity in the range from 50 to 300 SUS at F., from 4 to 12 volume percent of a lipophilic emulsifying agent selected from the group consisting of a fatty acid partial ester of sorbitan and sorbide, 5 to 20 volume percent of a hydrophilic emulsifying agent based on said lipophilic emulsifying agent comprising an ethylene oxide C alkylphenol adduct in mole ratios of from 10:1 to 40:1, 0.1 to 1.0 volume percent of a concentrate of a mono-(fl-hydroxyethyl) polybutene thiophosphonate in which said polybutene radical has a molecular weight from about 600 to 5,000, and a volatile corrosion inhibitor selected from the group consisting of amine nitrites and amine carboxylates in an amount ranging from 0.05 to 1.0 volume percent.

6. A fire resistant water-in-oil emulsion suitable for use as a hydraulic fluid according to claim 5 in which said lipophilic emulsifying agent is sorbitan monooleate, said hydrophilic emulsifying agent is nonylphenol polyoxyethanol, said thiophosphonate is mono-(B-hydroxyethyl) polybutene thiophosphonate in which said polybutene radical has a mean molecular weight of about 940 and which contains an effective anti-foam amount of a dialkyl silicone polymer.

References Cited by the Examiner UNITED STATES PATENTS 2,965,574 12/1960 Tierney et al 252-78 3,050,465 8/1962 Francis 252-77 X 3,087,956 4/1963 Lacoste et al. 260461.110

OTHER REFERENCES Surfonic Surface-Active Agents, technical bulletin of the Jefferson Chemical Co., Inc., 1958, pages 3 and 5.

LEON D. ROSDOL, Primary Examiner.

JULIUS GREENWALD, ALBERT T. MEYERS,

Examiners. R. D. LOVERING, Assistant Examiner. 

1. A FIRE RESISTANT WATER-IN-OIL EMULSION SUITABLE FOR USE AS A HYDRAULIC FLUID COMPRISING FROM 60 TO 40 VOLUME PERCENT OF WATER AND FROM 40 TO 60 VOLUME PERCENT OF AN OLEGINOUS BLEND CONTAINING A MAJOR PORTION OF A MINERAL OIL HAVING A VISCOSITY IN THE RANGE FROM 50 TO 300 SUS AT 100*F., FROM 1 TO 12 VOLUME PERCENT OF A LIPOPHILIC EMULSIFYING AGENT SELECTED FROM THE GROUP CONSISTING OF A FATTY ACID PARTIAL ESTER OF A 6 CARBON POLYGYDRIC ALCOHOL MONO- AND DI-ANHYDRIDE AND MIXTURE THEREOF, 5 TO 20 VOLUME PERCENT OF A HYDROPHILIC EMULSIFYING AGENT BASED ON SAID LIPOPHILIC EMULSIFYING AGENT COMPRISING AN ETHYLENE OXIDE C4-24 ALKYLPHENOL ADDUCT IN MODE RATIOS OF FROM 10:1 TO 40:1, 0.05 TO 2.5 VOLUME PERCENT OF A CONCENTRATE OF A MONO-(HYDROXYALKYL) HYDROCARBYL THIOPHOSPHONATE HAVING THE FORMULA: 